NEWS & PRESS

Cloud spotting seems to be growing in popularity as a hobby here on Earth. Now scientists studying the solar atmosphere are building their own collection of fascinating moving features that they’ve spotted in the Sun’s sky. The unusual solar prominences include a giant disc that rotates for several hours, feathery streamers as long as fifty Earths, a super-heated jet striking the top of a prominence and twisted ribbons flowing in opposite directions at a million kilometres per hour.

Rotating disc in solar prominence. Credit: NASA/SDO/Li/Smith/Aberystwyth UniversityThe features were discovered by Dr Xing Li and PhD student, Jeff Smith, of Aberystwyth University using the Atmospheric Imaging Assembly (AIA) telescope on board the Solar Dynamics Observatory (SDO) satellite. The findings have been presented at the RAS National Astronomy Meeting in St Andrews.

Prominences are – relatively – cold gaseous features, with temperatures around 5000 degrees Celsius compared to the surrounding the hot solar atmosphere of about 1-2 million degrees. They can be seen as towering features extending outwards from the Sun’s surface, often in the shape of a loop. They are called filaments when viewed against the solar disc, appearing as dark stripes because the cold gases they contain absorb the light emitted from below. Solar prominences and filaments supply most of the material released in coronal mass ejections, vast eruptions from the Sun's atmosphere that can cause space weather and create geomagnetic storms on Earth.

Rotating discs in solar prominences were first observed decades ago, using ground-based telescopes, and have puzzled solar physicists since. The new SDO observations of a rotating disc reveal that the feature covers a temperature range from a few thousand to one million degrees Celsius. Li and Smith believe that the rotation is caused by turbulence produced at the interface of two gases of enormously different temperatures.

Superheated jet striking a prominence. The jet is emitted to the left of the prominence and travels in an anticlockwise arc, striking the top of the prominence. NASA/SDO/Li/Smith/Aberystwyth University"We think the rotation is produced when hot gases enter a cold medium in an organised fashion. The magnetic field serves as a thermal barrier between the two media. The resulting rotation can last hours," said Li.

The persistent horizontal motion of feathery streamers from a solar prominence was observed by SDO over a period of more than 15 hours. Li and Smith believe that the likely cause is a large-scale, slow restructuring of the magnetic field through a process called magnetic reconnection.

In a further observation, lasting around three hours, a jet of superheated gases as hot as 1.5 - 2 million degrees Celsius was sucked from the coronal cavity surrounding a prominence and spiralled up along a helical path to strike the top of prominence 50 000 km high.

"The feat of the jet hitting the top of the prominence, and the distances involved, is comparable to a ballistic missile hitting a satellite in geostationary orbit!" said Li.

Finally the SDO imagery showed counter-streaming flows at more than a million kilometres per hour along a filament channel consisting of many very thin threads.

Bringing together more than 600 astronomers and space scientists, the RAS National Astronomy Meeting (NAM 2013) will take place from 1-5 July 2013 at the University of St Andrews, Scotland. The conference is held in conjunction with the UK Solar Physics (UKSP: www.uksolphys.org) and Magnetosphere Ionosphere Solar Terrestrial (MIST: www.mist.ac.uk) meetings. NAM 2013 is principally sponsored by the RAS, STFC and the University of St Andrews and will form part of the ongoing programme to celebrate the University’s 600th anniversary.

Meeting arrangements and a full and up to date schedule of the scientific programme can be found on the official website at http://www.nam2013.co.uk

The Royal Astronomical Society (RAS: www.ras.org.uk, Twitter: @royalastrosoc), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The Science and Technology Facilities Council (STFC: www.stfc.ac.uk, Twitter: @stfc_matters) is keeping the UK at the forefront of international science and tackling some of the most significant challenges facing society such as meeting our future energy needs, monitoring and understanding climate change, and global security. The Council has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar. It enables UK researchers to access leading international science facilities for example in the area of astronomy, the European Southern Observatory.

Founded in the 15th century, St Andrews is Scotland’s first university and the third oldest in the English speaking world. Teaching began in the community of St Andrews in 1410 and the University was formally constituted by the issue of Papal Bull in 1413. The University is now one of Europe’s most research intensive seats of learning – over a quarter of its turnover comes from research grants and contracts. It is one of the top rated universities in Europe for research, teaching quality and student satisfaction and is consistently ranked among the UK’s top five in leading independent league tables produced by The Times, The Guardian and the Sunday Times.

The University is currently celebrating its 600th anniversary and pursuing a £100 million fundraising campaign, launched by Patron and alumnus HRH Prince William Duke of Cambridge, including £4 million to fund the creation of an ‘Other Worlds’ Think Tank and Observatory. The new think tank and Observatory project will extend the University of St Andrews’ flagship work on extra-solar planets, and provide a creative environment for problem-focused research, education and continuing public engagement.